The present invention relates to pre-crash sensing systems for automotive vehicles, and more particularly, to pre-crash sensing systems having countermeasures operated in response to the length and width of a detected vehicle.
Auto manufacturers are investigating radar, lidar, and vision-based pre-crash sensing systems to improve occupant safety. Current vehicles typically employ accelerometers that measure vehicle body decelerations in the event of a crash. In response to accelerometers, airbags or other safety devices are deployed.
In certain crash situations it would be desirable to provide information before forces actually act upon the vehicle when a collision is unavoidable. Such information may include the position of a target vehicle relative to a source vehicle.
Remote sensing systems using radar are used in adaptive cruise control, collision avoidance and collision warning applications. These systems have characteristic requirements for false alarms. Generally, the remote sensing system reliability requirements for pre-crash sensing for automotive safety related systems are more stringent than those for comfort and convenience features, such as, adaptive cruise control. The reliability requirements even for safety related features vary significantly, depending upon the safety countermeasure under consideration. For example, tolerance towards undesirable activations may be higher for activating motorized belt pre-tensioners than for functions such as vehicle suspension height adjustments. Non-reversible safety countermeasures, including airbags, require extremely reliable sensing systems for pre-crash activation.
To meet wide-angle coverage requirements for pre-crash sensing purposes, multiple pulsed radar based sensing systems are being investigated for automotive applications. Multiple, pulsed radar sensor based systems with a wide field of coverage are available. Triangulation techniques with individual radar range measurements are used with multiple pulsed radar systems for object position estimation.
Threat assessment concepts based on the width and path of the host vehicle, and tracked objects are also available. These concepts do not properly account for the dimensions of the host and target vehicles. They also do not address the issue of impact situation classification. For example, they do not separate between those potential collisions in which the front of the host vehicle is involved, and those in which the sides of the host vehicle are involved.
The length and width of the host and target vehicles are important in deciding whether the accident is going to happen or whether it is going to be a near miss situation. Also, for countermeasure deployment decisions, such as nose-dipping, it is necessary to know if the front or sides of the host vehicle will be involved in the accidents.
It would therefore be desirable to provide a reliable method for determining the position of a target vehicle. It would also be desirable to provide a system that takes into consideration the size of the object including the length of the object in the activation of a countermeasure.
The present invention provides an improved pre-crash sensing system that reduces false activations and activates a countermeasure in response to the size of the object detected.
In one aspect of the invention, a pre-crash sensing system for a source vehicle having a source vehicle length and a source vehicle width that is coupled to a countermeasure system is described. The system includes an object sensor for generating an object distance signal, object relative velocity signal and an object classification signal. A controller is coupled to the object sensor. The controller determines a danger zone in response to the source vehicle length, source vehicle width and object length and object width. The source vehicle time interval is determined by the controller corresponding to the time the source vehicle is within the danger zone. The controller determines the object time interval corresponding to the time the object is within the danger zone. The controller determines a point of impact in response to the object time interval and the source vehicle time interval. The controller activates the countermeasure in response to the point of impact.
In a further aspect of the invention, a method for operating a pre-crash sensing system for a source vehicle having a source vehicle width and length having a countermeasure system, said method comprises: measuring a source vehicle speed; determining an object distance and object speed; determining an object classification with a vision system; determining an object length and object width corresponding to the object classification; determining a danger zone based on the source vehicle length, source vehicle width and object length and object width; determining a source vehicle time interval corresponding to the time the source vehicle is within said danger zone; determining an object time interval corresponding to the time the target vehicle is within said danger zone; determining a point of impact in response to the time interval, the source vehicle speed and object speed; and activating the countermeasure system in response to the point of impact.
One advantage of the invention is that the length and width of the sensed object may be taken into consideration. This is extremely useful if the object is another automotive vehicle such as a sport utility, car or truck. By knowing the size of the vehicle, different countermeasures and different countermeasure activation modes may be chosen.
Another advantage of the invention is that unintentional, inadvertent or unnecessary activations of countermeasure devices are minimized.